1. Field of the Invention
The invention relates to a liquid delivery system and control mounted to a granular material spreader mounted on a vehicle for synchronous dispensing of solid or granulated and liquid thawing materials onto a road. The solid or granular materials and the liquid materials are stored in separate vessels and moved to a delivery point for application to the road. The quantity of liquid supplied is synchronized to the rate of delivery of the granular material.
2. Description of the Prior Art
Spreader vehicles or spreader implements for distributing a thawing solution or traction enhancing materials on roads are known. Such spreader vehicles have a granular material delivery system and can include a liquid delivery system, wherein a gravity feed system or a liquid pump supplies thawing liquid from a tank carried by the vehicle. A granular and liquid material spreader is shown in W. Kupper, U.S. Pat. No. 4,442,979. The Kupper patent also shows synchronized delivery of both liquid and granular materials according to the speed of travel of the vehicle. Kupper can deliver only liquid, only granular material or a combination of the two, all proportional to the speed of the vehicle.
Neither Kupper nor any other prior art shows a liquid and granular delivery system using a hydraulic system which selectively varies the feed rate of the liquid material depending upon the extent to which hydraulic flow from the granular material delivery system is diverted to the liquid delivery system. None of the prior art shows a liquid delivery system which varies liquid feed rates from the synchronized feed rate by use of a liquid flow control valve to remove a selected amount of liquid from the liquid delivery system.
None of the prior art shows a variable feed rate of the granular material delivery system dependent on activation of and the feed rate of the liquid delivery system. The prior art does show a fixed reduction feed rate of granular material on activation of a liquid delivery system.
A. Kahlbacher, in U.S. Pat. No. 3,420,451, shows a dispenser for granular road salt which includes a liquid metering device. The metering device is driven by a mechanical cam system connected to the drive shaft of an auger type conveyor. The metering device is mounted in a supply duct to regulate the flow of liquid dependent on the speed of the vehicle. As in other prior art systems, a greater or lesser feed rate of liquid, than established by the granular delivery system, is not available without major adjustment to the liquid delivery system. The granular delivery system feed rate in all prior art but a commercial system built by A/S Alfred Thompson in Rejen, Denmark is unaffected by the mechanical connection to the liquid delivery system, resulting in excess use of granular material. In the A/S Alfred Thompson device, the granular material feed rate is set on activation of the liquid delivery system.
In G. Murray, et al. in U.S. Pat. No. 3,559,894, an aggregate spreading apparatus uses a belt conveyor instead of an auger conveyor. Other prior art granular salt spreaders have means for delivering liquid in combination with or separately from the granular material include: French Patents No. 2,229,812 and 2,378,132; West German Patent No. 3,712,452; and Swiss Patent No. 516,050.
A hydraulic drive and control system wherein the granular delivery system and the liquid delivery system are interconnected to vary both the granular and liquid feed rate separately has not been shown. W. Kupper combines a single hydraulic drive and delivery system which is incapable of varying feed rate of the liquid material. The feed rate is typically dependent on speed of the vehicle on which the spreading device is mounted. Some prior art systems do allow the operator to change the granular feed rate independent of vehicle speed. Gravity or electric liquid feed systems also exist which are not dependent on speed of the vehicle, but those systems do not synchronize granular and liquid feed rates.